A film capacitor is produced by covering a metal foil layer onto a film of a thermoplastic resin such as polypropylene or polyethylene terephthalate. Such a film capacitor is used, in electronic or electrical instruments, as, for example, a high-voltage capacitor, or a filter capacitor and a smoothing capacitor for various switching power sources, converters, inverters and others.
Film capacitors are required to have a high voltage endurance, particularly, a high initial voltage endurance even when a high voltage is applied to the capacitors in a broad temperature range, for example, the range of −40 to 90° C. The film capacitors may be used, particularly, at high temperature; thus, required is a film for a capacitor to which a high voltage can be applied at high temperature.
For example, Cited Document 1 discloses a biaxially oriented film for a capacitor that includes polyethylene-2, 6-naphthalene dicarboxylate, a polyolefin, and others. Cited Document 2 discloses a film for film-capacitor that is formed by laminating plural films which are produced using a T die and which include a thermoplastic resin.